• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.103-104
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• 2015

Solar energy has proven to be a potential clean energy source to help offset the large consumption of fossil. Nowadays, many research projects aim to enhance photovoltaic (PV) system performance and functionality. This research focuses on integrating self-monitor capability into dc-dc converters that control PV panels to detect a fault in series-connected PV cells, called hot spotting. A detection method using ac parameter characterization is proposed and its operation is examined through simulation.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.217-218
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• 2018

Droop control method is the conventional controller to solve the problem of current sharing error and voltage deviation that can occur in parallel connection of DC-DC converter. This paper compared V-I droop control with I-V droop control, which based on communication and confirmed the results through experiments.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.415-416
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• 2020

2상 인터리브드 기법은 DC-DC컨버터의 스위칭 주파수의 2배의 효과를 얻을 수 있어 전류 리플 감소와 효율 향상을 위해 널리 쓰이는 방법이다. 하지만, 인덕터 및 스위치 등의 물리적인 편차와 방열 성능차이 등으로 인한 상간의 전류 불평형 문제로 하나의 상에 스트레스가 집중되어 내구성이 저하되고 수명감소로 이어지는 단점이 있다. 본 논문에서는 인터리빙 기법에서 발생하는 전류 불평형 문제를 단일 센서를 사용한 제어기법으로 해결하고 그에 대한 타당성을 시뮬레이션을 통하여 검증하였다.

• Journal of Power Electronics
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• v.14 no.2
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• pp.265-270
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• 2014

In terms of power loss, a MOSFET has two advantages over an IGBT with an antiparallel diode: purely resistive without an offset voltage in conduction and no tail current at turn-off. However, the reverse recovery characteristic of the body diode is so poor that MOSFETs have not yet been available for high-voltage power converters with bidirectional power flow legs. This paper introduces how MOSFETs can be fully applied to high-voltage power converters with bidirectional power flow legs in order to achieve high efficiency. With a bidirectional DC-DC converter with one leg as the simplest example, the basic circuit topology and operating principle are described in detail. The high efficiency and stable operation of the proposed converter are validated through experiments with a 1.5 kW prototype.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.3
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• pp.145-150
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• 2013

A novel AC to DC PWM converters with unity input power factor are proposed to overcome the above shortcoming. The main function of these converters is to shape the input line current to force it exactly in phase with the input AC voltage. Therefore, the input power factor can be improved to near unity and the input current harmonics can be eliminated. In this paper, half-bridge converter with two active switches and two diodes are utilized for low-cost type UPS configuration. By having only two semiconductors in the current path at any time, losses can be reduced over the conventional boost topology. Also, this converter provides controllable dc-link voltage, high power factor, and low cost type converter by simple power circuits. Simulation results show that the proposed half-bridge converter/inverter control technique can be applied to single-phase low-cost type UPS systems successfully.

• Journal of Power Electronics
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• v.10 no.1
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• pp.21-26
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• 2010

The most important feature of the one-cycle control method is its excellent ability in line disturbance rejection. However, when it is used as a controller in dc-dc converters, it has an undesirable transient response. The voltage overshoot at the transient time, which usually exists in one-cycle controlled converters, is unwanted in many applications and it is sometimes hazardous. In this paper, it is shown that the combination of a one-cycle controller with a current mode controller, can improve the transient response and consequently the overshoot can be controlled. Therefore, the combined controller has the excellent line disturbance rejection of a one-cycle controller and the output current limiting capability of current mode controllers. Because in this scheme a one-cycle controller is the master controller, the problem of instability of current mode control, will not happen. By simulation and a practical prototype, the capability of the method is shown.

• Journal of Power Electronics
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• v.13 no.4
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• pp.647-655
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• 2013

In this paper, an approach to reduce the common-mode voltage and to eliminate narrow pulse for implemented AC-DC matrix converters is presented. An improved space vector modulation (SVM) strategy is developed by replacing the zero space vectors with suitable pairs of active ones. Further, while considering the commutation time, the probability of narrow pulse in the conventional and proposed SVM methods are derived and compared. The advantages of the proposed scheme include: a 50% reduction in the peak value of the common-mode voltage; improved input and output performances; a reduction in the switching loss by a reduced number of switching commutations and a simplified implementation via software. Experimental results are presented to demonstrate the correctness of the theoretical analysis, as well as the feasibility of the proposed strategy.

• Journal of Power Electronics
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• v.9 no.4
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• pp.517-525
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• 2009

42V electrical power systems are on their way to replacing the present l4V systems in automobiles and 42V/14V dual voltage systems have been proposed to provide backward compatibility with the existing components for the 14V systems. A synchronous buck/boost converter is an attractive topology for 42V/14V dual voltage systems since it offers the possibility of bi-directional operation without additional components. In this paper, transient currents generated during converter startup or changes in operation modes between buck and boost are analyzed and a cost effective solution to remove the transient currents is proposed. The validity of the proposed control strategy is investigated through simulation and experiment with bi-directional converters.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.152-155
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• 2009

In high power application, PFC(Power Factor Correction) pre-regulators are generally required. PFC pre-regulators could achieve unity power factor, reduce line input current harmonics and utilize full line power. Interleaving PFC converters could reduce input ripple current, output capacitor ripple current and inductor size. With this closed loop interleaving method, both two phase converters are working at the boundary between continuous and discontinuous mode and accurate 180 degree phase shift is achieved. Implementation of this strategy could be easily integrated to the control chip. Finally, experimental results of a two-phase interleaved boost PFC are presented to verify the discussed features.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.74-75
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• 2010

As global warming due to burning fossil fuels and natural resource depletion issues have emerged, the development of renewable energy sources such as photovoltaics (PV) has been brought to recent interest. Amongst the vast efforts to harvest and convert solar energy into electricity, the module integrated converters (MIC) has become a worthy topic of research for grid-connected photovoltaic systems. Due to the required high-boosting qualities, only a restricted amount of DC/DC converter topologies can be applied to MICs. This paper investigates the possibility of a tapped-inductor boost converter as a candidate for PV MICs. A dual-inductor interleaving scheme operating slightly above the boundary of the two conduction modes (BCM) is suggested for reduction of input current ripple and minimization of component stress. A digital controller is used for implementation, assuring maximum power tracking and transfer while providing sufficient computational space for other grid connectivity applications, etc. For verification, a 200W converter is designed and simulated via computer software including component losses. High efficiency over a wide power range proves the feasibility of the proposed PV MIC system.